Update 3:56 p.m. This editorial has been updated to reflect news that Senate Majority Whip John Cornyn told reporters Monday that he agrees that firing Mueller would be a mistake.

Over the weekend, a diverse assortment of Republican senators did President Donald Trump and the country a service in issuing a direct warning to the president: His attacks on the FBI and on the inquiry by special counsel Robert Mueller must end.

If they don't, Trump risks destroying his own presidency, inflicting enormous damage to the office he holds and the nation he leads.

Trump began the weekend by joyously exulting in Friday's firing of Andrew McCabe, the former FBI deputy director whose retirement was scheduled to be effective two days later.

Trump also attacked former FBI Director James Comey, calling him a liar. Then he accused the FBI of widespread corruption at its highest levels, a claim he later amplified to include corruption by the Justice and State departments during, and perhaps since, the election.

As the House Intelligence Committee has concluded, there was no collusion between Russia and the Trump Campaign. As many are now finding out, however, there was tremendous leaking, lying and corruption at the highest levels of the FBI, Justice & State. #DrainTheSwamp

The inquiry is also examining whether the Trump campaign, the Trump family or others in his orbit knew about the effort and whether they aided it. There has been no evidence of actual collusion presented, but already Trump's former campaign manager, a former foreign policy adviser and the former general he elevated to lead the National Security Council— against explicit warnings from outgoing President Barack Obama — have been indicted.

In response, Trump stepped up his assault on Mueller. Despite the investigation's more than 20 indictments or guilty pleas so far, Trump twice called it a "witch hunt" over the weekend and said it should never have been authorized.

The attacks were so sudden, and with such sustained ferocity, members of his own party recoiled. Trump would risk destroying his presidency were he to follow through and fire Mueller, some said.

"People see that as a massive red line that can't be crossed," said Sen. Jeff Flake, R-Ariz. "I hope that the pushback is now to keep the president from going there."

These warnings should be amplified by others in Congress. Senate Majority Whip John Cornyn of Texas, told reporters on Monday during a brief interview in the Capitol that he agreed with his colleagues' statements from the weekend that it'd be a mistake to fire Mueller. Others should speak out as well.

We don't know what the Mueller inquiry will ultimately say about the 2016 campaign. But America deserves to know the whole story. An abrupt halt to his work will only create a firestorm that not even the president will likely be able to put out.